Floor portals allow you to teleport on top of walls

[mallo]

GZDoom version: g3.2pre-110-g60cb457

If you bump into a two-sided wall while being partially in a portal you will automatically get teleported on top of it, no matter the height, kind of as if you noclipped on top of it.

Here's an example map. It has a portal and a huge wall. If you walk into the portal and then bump into the wall, you'll get teleported on top of it.

[Graf Zahl]

Don't you just love Doom's crappy "physics" code...?

[Major Cooke]

I can't help but wonder if it actually would be worth the time occasionally trying to prototype some way to change the physics code in an unstable branch, though something tells me that this would have to outright rip the engine to tiny little shreds in order to achieve.

[Graf Zahl]

The actual issue here - as with many, many other glitches - is how the engine treats z as an afterthought and not as an integral part of position calculations.
Trying to change this will alter one of the most fundamental properties of how movement works in Doom and indeed rip the engine to tiny little shreds.

[AFADoomer]

Would it be worth having a parallel physics system with proper handling that could be chosen by mod authors via MAPINFO? Or would maintaining two overlapping physics systems just be a crazy thing to even attempt?

[Graf Zahl]

It wouldn't be really necessary to implement a completely new physics system. The actual problem is one particular function and what it calls (i.e. P_TryMove plus P_XYMovement and P_ZMovement) If you look at that function you'll see that it works entirely in 2D and only gets called with a 2D destination. That's the underlying problem here: The z-coordinate is not a natural part of movement but implicitly extrapolated. To fix that everywhere will be a major task. If I ever could find a way to do that without messing up the quirks of Doom's movement system I'd happily do.

[Caligari87]

As a casual user, one of the main roadblock issues I've seen crop up over the years is the physics engine. For what little it's worth, I've thought for a *long* time that GZDoom should work towards divorcing itself from Doom's physics quirks and settle for "close enough" pseudo-emulation (which I'm sure can be achieved in a proper physics engine).

Granted I know I'm probably in the extreme minority here, and as-is GZDoom gets enough hate outside our community for not being "vanilla enough." Just saying I feel the physics engine has always been one of the biggest things holding GZDoom back from being more than just a Doom engine.

[Graf Zahl]

Trust me, that will NEVER happen!

[Graf Zahl]

Fixed. But keep in mind that with the fixed code you won't be able to walk out of that portal pit either, because the step height would be 32, which is more than the maximum of 24.